Pitot Tube Flow Meter

Pitot Tube Flow Meter

Feature Description
Non-intrusive Measurement Clamp-on installation, no pipe cutting required
No Pressure Loss No obstruction inside the pipeline
High Accuracy & Repeatability Up to ±0.5% for transit-time type
Working Principle Based on transit-time and Doppler effect
Low Maintenance No moving parts, long service life
Application Flexibility Suitable for large pipe sizes and wide range of liquids

Key Features

Direct Velocity Measurement
  • Measures fluid velocity directly
  • Uses stagnation & static pressure difference
Bernoulli’s Principle
  • Based on Bernoulli’s theorem
  • Converts pressure difference into velocity
Simple Probe Design
  • Impact (total pressure) port
  • Static pressure port
No Moving Parts
  • High reliability
  • Low maintenance requirement
Low Pressure Drop
  • Minimal energy loss
  • Does not obstruct flow significantly
Point Velocity Measurement
  • Measures at a specific point
  • Not a direct average flow measurement
Differential Pressure Based
  • Requires DP measurement
  • Uses manometer or DP transmitter
High Velocity Suitability
  • Ideal for gases
  • Works well with clean liquids
Insertion Type Installation
  • Can be inserted into pipelines
  • No major modification required
Wide Operating Conditions
  • Handles high temperature
  • Handles high pressure
Flow Profile Correction
  • Needs multiple readings
  • Improves average flow accuracy
Compact & Lightweight
  • Easy to install
  • Convenient handling

Working Principle

1. Fluid enters the pipe
o The fluid flows with velocity vvv.
2. Impact (stagnation) pressure measurement
o The front opening of the Pitot tube faces the flow.
o Fluid comes to rest → velocity becomes zero.
o This pressure is called stagnation pressure (Pₜ).
3. Static pressure measurement
o Side holes measure the static pressure (Pₛ) of the flowing fluid.
4. Pressure difference generated
o Difference between stagnation and static pressure:

ΔP = Pt – Ps

5. Velocity calculation
o Using Bernoulli’s equation, velocity is calculated:

v = sqrt( (2 (Pt – Ps)) / ρ )

6. Flow rate determination
o Once velocity is known:

Q= A . v

o Where A = cross-sectional area of pipe

Industrial Applications

HVAC Systems
  • Used for air flow measurement
  • Measures velocity in ducts
  • Applicable in heating, ventilation & air conditioning
Power Plants
  • Measures flue gas flow
  • Used in boilers and chimneys
Aerospace Industry
  • Used in aircraft systems
  • Helps determine airspeed
Oil & Gas Industry
  • Measures gas flow in pipelines
  • Used in processing units
Water Supply Systems
  • Used in large pipes and channels
  • Estimates flow velocity
Chemical Industries
  • Measures clean gases and liquids
  • Used in reactors and pipelines
Compressed Air Systems
  • Monitors air flow
  • Used in compressors & pneumatic systems
Environmental Monitoring
  • Measures air velocity in stacks
  • Used for emission and pollution studies

Technical Specifications

Parameter Typical Range / Value Description
Measurement Principle Based on Bernoulli’s principle Uses pressure difference to determine velocity
Measured Quantity Velocity, Flow rate Primary output is velocity
Velocity Range 5 to 300 m/s Works best at higher velocities
Flow Range Depends on pipe size Derived from velocity
Accuracy ±2% of full scale Varies with calibration
Repeatability ±0.5% High consistency
Pressure Range Up to 17 bar (or higher with design) Suitable for industrial use
Temperature Range -50°C to 600°C Depends on material
Fluid Type Clean gases & liquids Not ideal for dirty fluids
Pipe Size DN25 to DN2000+ Suitable for large ducts/pipes
Output Signal 4–20 mA, Digital (Modbus, HART) For industrial control systems
Power Supply 18–30 V DC For transmitters
Installation Type Insertion type Can be installed online
Pressure Loss Very low (negligible) Minimal energy loss
Response Time Fast Instant pressure sensing
Material Stainless steel (SS304/SS316) Corrosion resistant
Mounting Flanged / Threaded / Compression fitting Flexible installation
Calibration Factory calibrated May need periodic check
Minimum Velocity ~5 m/s Below this → poor accuracy
Data Logging Up to millions of records (smart transmitters) Optional feature
Maintenance Low No moving parts